6,772 research outputs found
Further SEASAT SAR coastal ocean wave analysis
Analysis techniques used to exploit SEASAT synthetic aperture radar (SAR) data of gravity waves are discussed and the SEASAT SAR's ability to monitor large scale variations in gravity wave fields in both deep and shallow water is evaluated. The SAR analysis techniques investigated included motion compensation adjustments and the semicausal model for spectral analysis of SAR wave data. It was determined that spectra generated from fast Fourier transform analysis (FFT) of SAR wave data were not significantly altered when either range telerotation adjustments or azimuth focus shifts were used during processing of the SAR signal histories, indicating that SEASAT imagery of gravity waves is not significantly improved or degraded by motion compensation adjustments. Evaluation of the semicausal (SC) model using SEASAT SAR data from Rev. 974 indicates that the SC spectral estimates were not significantly better than the FFT results
A Machine-Checked Formalization of the Generic Model and the Random Oracle Model
Most approaches to the formal analyses of cryptographic protocols make the perfect cryptography assumption, i.e. the hypothese that there is no way to obtain knowledge about the plaintext pertaining to a ciphertext without knowing the key. Ideally, one would prefer to rely on a weaker hypothesis on the computational cost of gaining information about the plaintext pertaining to a ciphertext without knowing the key. Such a view is permitted by the Generic Model and the Random Oracle Model which provide non-standard computational models in which one may reason about the computational cost of breaking a cryptographic scheme. Using the proof assistant Coq, we provide a machine-checked account of the Generic Model and the Random Oracle Mode
The Physics of Heavy Flavours at SuperB
This is a review of the SuperB project, covering the accelerator, detector,
and highlights of the broad physics programme. SuperB is a flavour factory
capable of performing precision measurements and searches for rare and
forbidden decays of , , and
particles. These results can be used to test fundamental symmetries and
expectations of the Standard Model, and to constrain many different
hypothesised types of new physics. In some cases these measurements can be used
to place constraints on the existence of light dark matter and light Higgs
particles with masses below . The potential impact of the
measurements that will be made by SuperB on the field of high energy physics is
also discussed in the context of data taken at both high energy in the region
around the \Upsilon({\mathrm{4S}})$, and near charm threshold.Comment: 49 pages, topical review submitted to J. Phys
An Analysis of the Shapes of Interstellar Extinction Curves. V. The IR-Through-UV Curve Morphology
We study the IR-through-UV interstellar extinction curves towards 328
Galactic B and late-O stars. We use a new technique which employs stellar
atmosphere models in lieu of unreddened "standard" stars. This technique is
capable of virtually eliminating spectral mismatch errors in the curves. It
also allows a quantitative assessment of the errors and enables a rigorous
testing of the significance of relationships between various curve parameters,
regardless of whether their uncertainties are correlated. Analysis of the
curves gives the following results: (1) In accord with our previous findings,
the central position of the 2175 A extinction bump is mildly variable, its
width is highly variable, and the two variations are unrelated. (2) Strong
correlations are found among some extinction properties within the UV region,
and within the IR region. (3) With the exception of a few curves with extreme
(i.e., large) values of R(V), the UV and IR portions of Galactic extinction
curves are not correlated with each other. (4) The large sightline-to-sightline
variation seen in our sample implies that any average Galactic extinction curve
will always reflect the biases of its parent sample. (5) The use of an average
curve to deredden a spectral energy distribution (SED) will result in
significant errors, and a realistic error budget for the dereddened SED must
include the observed variance of Galactic curves. While the observed large
sightline-to-sightline variations, and the lack of correlation among the
various features of the curves, make it difficult to meaningfully characterize
average extinction properties, they demonstrate that extinction curves respond
sensitively to local conditions. Thus, each curve contains potentially unique
information about the grains along its sightline.Comment: To appear in the Astrophysical Journal, Part 1, July 1, 2007. Figures
and Tables which will appear only in the electronic version of the Journal
can be obtained via anonymous ftp from ftp://ftp.astronomy.villanova.edu .
After logging in, change directories to "fitz/FMV_EXTINCTION". A README file
describes the various files present in the director
Surface and Temporal Biosignatures
Recent discoveries of potentially habitable exoplanets have ignited the
prospect of spectroscopic investigations of exoplanet surfaces and atmospheres
for signs of life. This chapter provides an overview of potential surface and
temporal exoplanet biosignatures, reviewing Earth analogues and proposed
applications based on observations and models. The vegetation red-edge (VRE)
remains the most well-studied surface biosignature. Extensions of the VRE,
spectral "edges" produced in part by photosynthetic or nonphotosynthetic
pigments, may likewise present potential evidence of life. Polarization
signatures have the capacity to discriminate between biotic and abiotic "edge"
features in the face of false positives from band-gap generating material.
Temporal biosignatures -- modulations in measurable quantities such as gas
abundances (e.g., CO2), surface features, or emission of light (e.g.,
fluorescence, bioluminescence) that can be directly linked to the actions of a
biosphere -- are in general less well studied than surface or gaseous
biosignatures. However, remote observations of Earth's biosphere nonetheless
provide proofs of concept for these techniques and are reviewed here. Surface
and temporal biosignatures provide complementary information to gaseous
biosignatures, and while likely more challenging to observe, would contribute
information inaccessible from study of the time-averaged atmospheric
composition alone.Comment: 26 pages, 9 figures, review to appear in Handbook of Exoplanets.
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Renaissance of the ~1 TeV Fixed-Target Program
This document describes the physics potential of a new fixed-target program
based on a ~1 TeV proton source. Two proton sources are potentially available
in the future: the existing Tevatron at Fermilab, which can provide 800 GeV
protons for fixed-target physics, and a possible upgrade to the SPS at CERN,
called SPS+, which would produce 1 TeV protons on target. In this paper we use
an example Tevatron fixed-target program to illustrate the high discovery
potential possible in the charm and neutrino sectors. We highlight examples
which are either unique to the program or difficult to accomplish at other
venues.Comment: 31 pages, 11 figure
On-the-Fly Trace Generation and Textual Trace Analysis and Their Applications to the Analysis of Cryptographic Protocols
Conceptualising sustainability in UK urban Regeneration: a discursive Formation
Despite the wide usage and popular appeal of the concept of sustainability in UK policy, it does not appear to have challenged the status quo in urban regeneration because policy is not leading in its conceptualisation and therefore implementation. This paper investigates how sustainability has been conceptualised in a case-based research study of the regeneration of Eastside in Birmingham, UK, through policy and other documents, and finds that conceptualisations of sustainability are fundamentally limited. The conceptualisation of sustainability operating within urban regeneration schemes should powerfully shape how they make manifest (or do not) the principles of sustainable development. Documents guide, but people implement regenerationāand the disparate conceptualisations of stakeholders demonstrate even less coherence than policy. The actions towards achieving sustainability have become a policy āfixā in Eastside: a necessary feature of urban policy discourse that is limited to solutions within market-based constraints
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